An elevated rate of glycolysis has long been known to characterize many types of tumors, but the molecular mechanism(s) by which this change occurs and the possible role of increased glycolysis in tumorigenesis are still poorly understood. Cells transformed by Rous sarcoma virus (RSV) transport glucose and glycolyze at an elevated rate. RSV-transformed cells present a very favorable system for studying the increased glycolytic metabolism because of the availability of wellmatched normal and malignant cells, the existence of temperature-conditional and "partial" transformation mutants of RSV and because of recent advances in understanding the mechanism of RSVinduced transformation. Our research is aimed at elucidating the molecular mechanism and biological significance of the increased glycolysis seen in RSV-transformed cells. We propose to characterize key enzymes of glycolysis with respect to activity, amount, isozyme type, secondary modifications and intracellular localization. We also will isolate cell mutants defective in specific steps in glycolysis. These mutants should prove useful in determining the role of glucose metabolism in tumor formation, the regulation of glycolysis in normal and malignant cells and in studying the regulation of the genes coding for the enzymes of glucose metabolism.